Audio portion of dash downloads slow

[Nick Payne]

On 14/03/2022 09:30, VeniVidiVideo wrote:
> On Mar 13, 2022, at 5:45 PM, Nick Payne <njhp94 at gmail.com> wrote:
>> When I download a program with GiP using dash rather than hls, the initial separate download of the audio always comes down at only somewhere between 5% and 10% of the speed that I get when the video portion of the download is happening. Do other users see the same? This is with the latest v3.29 GiP.
> 
> Did the audio actually download in much less time than the video, overall?  So you're mainly concerned about the reported download speeds?
> 
> If so, it's possible that the audio, being much smaller than the video, is having its download speed calculated from many fewer samples, so it is less accurate.  Its measurement would also be drastically more affected by any startup and/or shutdown overhead that is included in the download time.  No guarantees, but as long as the audio is actually downloading in substantially less time than the video the problem may simply be in how these speeds are being calculated.
> 

No, here's an example of the quite different speeds for the audio and 
video portions of a dash download - the 158Mb of audio took 31 minutes 
to download, and the 3536Mb of video took 1hr 2min, which means that the 
video portion downloaded at just over 14 times the speed of the audio 
download. If the audio had downloaded at the same speed as the video, 
the entire download would have completed in about 2/3 of the time it 
actually took. I see the same audio/video download speed difference for 
every dash download.

A second, and quite unrelated problem is that the estimated file sizes 
for fhd 1080p downloads are always too high by a factor or three or four 
- unlike 720p downloads, where the estimate is usually accurate within 
20% or so. Again, see the example below, where GiP's estimate for the 
video size was 10339Mb, but the actual size for the successfully 
completed download was 3536Mb. I think every fhd download I've done has 
had the same wildly inaccurate estimated size.

=========================================================================
INFO: Downloading tv: 'Snooker: Welsh Open: 2022 - 14. The Final - Part 
2 (m00158vr) [original]'
INFO: Trying 'dashfhd1' mode: attempt 1 / 3
INFO: ffmpeg version string = 4.3.3-0+rpt2+deb11u1
INFO: ffmpeg version number = 4.3
INFO: File name prefix = Snooker_Welsh_Open-s15e14-The_Final_-_Part_2
INFO: Begin downloading at: 0.00 MB (00:00:00) [1]
INFO: Downloaded: 158.00 MB (02:42:25) [2538] in 00:31:30 @ 0.67 Mb/s 
(dashfhd1/cf) [audio]
INFO: Begin downloading at: 0.00 MB (00:00:00) [1]
   3.3%   341.30 MB / ~10339.76 MB (00:09:01 / 02:42:25) [  141 / 2538] 
@   9.4 Mb/s ETA: 02:22:13 (dashfhd1/cf) [video]
[...]
INFO: Downloaded: 3536.83 MB (02:42:25) [2538] in 01:02:04 @ 7.60 Mb/s 
(dashfhd1/cf) [video]
INFO: Converting to MPEG-TS
[...]
=========================================================================

Nick